OCEANIC CIRCULATION 129 



in the North Pacific we have a similar vertical 

 circulation due to the same causes as in the 

 great Southern Ocean, but owing to the less 

 extent of the water surface, and the restricted 

 communication with the Arctic Ocean, the 

 effect upon the deeper waters of the ocean 

 basins is not so pronounced. 



The vertical movements of ocean water are 

 brought about (1) by the pull of winds on the 



Fia. 6. — Diagram showing the effect of wind on lee and windward shores. 



surface water resulting in up welling, (2) by 

 differences in salinity between different layers 

 produced by precipitation and evaporation, 

 and (3) by differences of density due to changes 

 of temperature. 



Upwelling is most marked whenever the 

 winds blow from the land towards the open 

 ocean ; the deeper water, having usually a 

 lower salinity and a lowxr temperature than the 

 water driven before the wind, is thus brought 

 to the surface. On the other hand the water 



